Thermal Energy

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Thermal Energy
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Temperature

• Kinetic energy is the energy of motion
• Temperature is the measure of the average value
  of kinetic energy of the molecules in a
  substance.
• The more kinetic energy the molecules have the
  higher the temperature.
• When objects increase or decreases their kinetic
  temperature expansion or contraction occurs.

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Measuring Temperature

• Thermometers use the expansion and contraction of
  materials used to measure temperature.
• Temperature scales include Fahrenheit and Celsius
• Celsius
• Fahrenheit

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Converting

• Fahrenheit to Celsius
• C 5/9 (F-32)
• Let's try converting 68 degrees
• Farenheit to celsius 5/9(68-32)
• Step 1 68 less 32 is 36Step 2 5 divided by 9
  is 0.5555555555555Step 3 multiply the repeating
  decimal by 36Step 4 your solution is 20

• Celsius to Fahrenheit
• Convert 20 degrees Celsius to Farenheit to check
  your work.
• 9/5C 32Step 1 9 divided by 5 is 1.8Step 2
  1.8 multiplied by 20 is 36Step 3 36 plus 32 68

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Conversion Problems

• 92 oF _______oC 103 oC ______ oF
• 19 oF _______oC -38 oC ______ oF
• 108 oF _______oC 102 oC ______ oF
• 102 oF _______oC -13 oC ______ oF
• 32 oF _______oC 69 oC ______ oF

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Thermal Energy and Heat

• Thermal energy TOTAL energy of all of the
  particles
• Heat thermal energy moving from a warmer object
  to a cooler object, trying to reach thermodynamic
  equilibrium

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Heat Transfer

• Always trying to reach Thermodynamic Equilibrium
• Heat is transferred (moves) in only one
  direction from a warmer object to a cooler
  object.
• Hot coffee cools to room temp because the heat of
  the coffee is transferred to the cooler
  temperature of the room.
• A cold glass of Iced tea soon warms up to the
  surrounding room temperature because the warmer
  temperature of the rooms surroundings is
  transferred to the colder glass of iced tea
  thereby warming it up.
• Heat is transferred in one of three ways
• Conduction, Convection and Radiation

Conductor a material that transfers heat well
metal, tile, glass Insulator a material that
does not transfer heat well air, carpet, wood
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Cup gets cooler while hand gets warmer
5. Heat a. The flow of thermal energy from
one object to another.
b. Heat always flows from warmer to cooler
objects.
Ice gets warmer while hand gets cooler
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Convection

• Convection is the transfer of heat by the actual
  movement of the warmed matter. Heat leaves the
  coffee cup as the currents of steam and air rise.
  
• Convection is the transfer of heat energy in a
  gas or liquid by movement of currents.
• Example convection is responsible for making
  macaroni rise and fall in a pot of heated water.
  The warmer portions of the water are less dense
  and therefore, they rise. Meanwhile, the cooler
  portions of the water fall because they are
  denser.

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Conduction

• Conduction is the transfer of energy through
  matter from particle to particle.
• It is the transfer and distribution of heat
  energy from atom to atom within a substance.
• Example A spoon in a cup of hot soup becomes
  warmer because the heat from the soup is
  conducted along the spoon.

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Radiation

• Radiation Electromagnetic waves that directly
  transport ENERGY through space.
• Sunlight is a form of radiation that is radiated
  through space to our planet without the aid of
  fluids or solids.

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Conduction, Convection Radiation
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Specific Heat

• the amount of energy required to raise the
  temperature of 1 kg of the object 10K.
• The unit is Joules/ Kg x o K
• Change in energy Mass x Specific Heat x change
  in Temp
• How much heat is required to raise the
  temperature of 5Kg of water 10oK? (Specific heat
  of water is 4,180 J/KgoK)
• Change in Energy 5 Kg x 4,180 J/KgoK x 10oK
• E
  209,000 J

E 50 g x .46 J / g oK x 80 oK 1840 J
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• What are the 3 ways that energy can transfer?
  Give 3 examples and what substances can each be
  transferred?